#include <functional> // std::bind, std::plus, std::placeholders, std::is_bind_expression
#include <iostream> // std::cout, std::boolalpha

int main() {
  using namespace std::placeholders; // introduces _1
  auto increase_int = std::bind(std::plus<int>(), _1, 1);

  std::cout << std::boolalpha;
  std::cout << std::is_bind_expression<decltype(increase_int)>::value
            << '\n'; // true

  return 0;
}
